The heat treatment of steels comprises the heating and cooling of the metal. The processes carried out are done to change their mechanical and physical properties, without letting it change its shape.

Generally, heat treatment processes are carried out for strengthening materials. However, most industries employ them for altering some mechanical properties of the metals such as improving machining, formability, etc. When it comes to its application, heat treatments are utilized metallurgically. Still, heat treatment of metals can also be used in the manufacturing of aluminum, steel, glass, and countless other materials.

The heat treatment process involves the use of colling or heating, usually to extreme temperatures, to achieve the desired result. These processes, when coupled, not only help in the manufacturing process but also improve the product, its performance, and its characteristic in many ways.

Hardening

Hardening involves heating of steel. It’s maintained at a suitable temperature until all pearlite is transformed into austenite, and then it is quenched in water or oil. The temperature where austenitizing rapidly takes place is dependent upon the carbon content in the steel used. The heating time ought to be raised, making sure that the core is converted into austenite. The microstructure of a steel part is cementite, martensite, or ferrite.

Tempering

Tempering comprises of heating steel that has been adequately hardened and quenched so that the metal can be equilibrated. The hardness and durability achieved depend upon the temperature. Higher temperatures will result in low hardness and high ductility. Low tempering temperatures will result in low ductility, but high strength and hardness.

Generally, appropriate tempering temperatures are picked, which are useful in achieving the desired level of durability and hardness. Tempering is done on all carbon steels that were hardened to reduce their brittleness so that they can be used for desired applications.

Annealing

Annealing involves treating steel up to a high temperature and then cooling it very slowly to room temperature. Following this process results in achieving a microstructure that possesses high ductility and toughness, but low hardness. This heat treatment process is performed by heating the component to an appropriate temperature, soaking it in at that same environment, and then shutting off the furnace (while the element is still inside).

Note: Steel is annealed before being processed by cold forming. It’s done to reduce the requirements of energy and load. Also, to enable the metal to undergo large strains without failure.

Normalizing

Normalizing includes heating the steel and then storing it at that temperature for a while. It’s followed by cooling it in the air. The resulting microstructure is a mixture of cementite and ferrite, which have greater strength and hardness but reduced ductility. Normalizing is done on structures and components which will be exposed to machining because it improves the machinability of carbon steels.